The effect of preparation temperature in oxygen on the structure and catalytic performance of LaSrCoO4 were studied. It was found that the active species in the LaSrCoO4 increased due to the formation of small particles leading to the increased active lattice oxygen and the improved catalyitic oxidation activity.
We have examined the oxygen relaxation and oxide ion conduction in yttria stabilized cubic zirconia, and the influence of the doped ceria content. Two maxima of the internal friction (IF) were observed for some CeO2 doped cubic Zr0.8-xCexY0.2O1.9 ceramics in the temperature range of 25∼420°C and at 9Hz using forced torsion method. The ceria addition reduced the amplitude of IF and the oxide ion conduction of Zr0.8-xCexY0.2O1.9. The result indicated that the doped CeO2 reduced the mobility of oxygen in yttria stabilized cubic zirconia even with the same concentration of defects.
The relationship between anelastic property and chemical species (F, OH) in calcium-containing apatite structure was investigated by the dynamic elastic technique. The internal friction and dynamic modulus of two apatite-type ceramics of hydroxylapatite (HAP) and fluoroapatite (FAP) were measured by using a forced torsion apparatus. The internal friction (IF) amplitude of about 0.01 was observed for HAP in the temperature range of -50 to 100°C. However, no IF appeared for FAP, in which hydroxyl-group was replaced by fluorine. The modulus of HAP showed the decrease corresponding to the IF amplitude. The author discussed that the dynamic relaxation of hydroxyl-group was evolved with the anelastic phenomenon of the apatite-structured material.
Ni-based superalloys are commonly used in hot gas path parts such as turbine blades because of their higher strength under high temperature. Their high strength results from an intermetallic compound such as a cubical γ' phase precipated in a γ phase. However, the γ' phase tends to show coarsening and lafting. The re-heat process has been adopted to repair the creep damage in the Ni-based superalloys. The re-heat process can restore the γ' phase by carrying out thermal cycles with an appropriate combination of temperature and duration. In this report, we focused on creep damage under the bending load. First, the creep constitutive law was developed to calculate creep strain more accurately. Then, we investigated the relationships between the effect of the re-heat process and creep crack initiation under the bending load through a mock-up creep test. The time-dependent hardening law was selected as a creep constitutive law. The calculated creep deformation showed relatively good correspondence with the results of uni-axial and mock-up creep tests. Also, creep crack initiation seemed to be controlled by the re-heat process at an appropriate stage. Re-heated specimens showed critical creep deformation, corresponding to creep crack initiation, about half that of virgin specimens. This seemed to be because of transgranular precipitation, not all of which can be removed using the re-heat process. In uni-axial creep tests, we found some critical value for cumulative creep strain, which causes harmful precipitation during the re-heat process. Therefore, we conclude that creep damage in Ni-based superalloys can be repaired effectively using the re-heat process before cumulative creep strain reaches a critical value that is restrained by the initiation of harmful precipitation or creep cracks.
Low cycle fatigue tests were performed for a low alloy steel, JIS SFVQ1A, used for pressure vessels of nuclear power plants. The effect of pre-strain history on the small crack initiation and growth was investigated in detail using cellulose acetate replicas. Under the tests in which the total strain range, Δε, is constant, surface crack length, 2c, was smaller for the tests with larger Δε due to the different numbers of small crack initiation and coalescence. The pre-strain histories were applied at Δε of 8 or 16% with its fatigue usage factor, UF, of less than 0.2, followed by fatigue loading at Δε = 2% until fracture. In these tests, the relationships between 2c and UF agreed with each other unless crack coalescence occurred. The scatter in fatigue life was attributed to the coalescences of small cracks. Fracture mechanics approach was applied to predict the fatigue lives and to characterize the growth behavior of small fatigue cracks.
The strength of torsional pre-strained specimen of aluminum was investigated. After torsion, the hardness of the specimen varied from surface layer to center section in cross sectional area. The tensile strength and fatigue limit were improved after application of the pre-strain, and these were related to the surface hardness. The fracture surfaces of fatigued specimens were different depending on the pre-strained level. Also, the application of the pre-strain affected on the crack growth direction and the detailed crack growth modes.
Mechanical tests are necessary to evaluate the deformation behavior of various materials. In particular, it is require that low- or non-destructive evaluation methods such as in-line inspection, which are employed in industries where less time and effort method is required. In this study, a spherical indentation method is developed to evaluate the mechanical properties of viscoelastic materials. The indentation method which can measure the Young's modulus of soft elastomer with finite thickness is applied to evaluate soft viscoelastic materials. The three-element solid model which can express strain rate dependency and stress relaxation is adopted as the constitutive model of the materials. The viscoelastic parameters of the three-element solid model are evaluated by defining the deformation resistance modulus, which depends on the indentation method. The applicability of the method is verified by comparing the parameters evaluated by both tensile and indentation tests. The results show that viscoelasticity can be evaluated as well as elasticity by the proposed low-destructive spherical indentation method.
Slurry scattering technique has been widely accepted to fix moving sand. By using organic slurry that has high water retention capacity, it seems that the vegetation on the desert may be realized. However, the organic material in the slurry, for example hydrophilic polyurethane, is easily decomposed by UV irradiation. In addition, the strength of UV ray is extremely strong on the desert. In this study, we found that the UV resistance of organic slurry can be effectively controlled through using a decomposition control agent. The decomposed products are nontoxic and environmentally friendly. By mixing Hindered Amine Light Stabilizer (HALS) as a decomposition control agent in the slurry with the ratio of 0.015%, 0.5∼0.7%, and 1.0%, the mass loss due to the ultrasonic irradiation was decreased to less than 20% of the mass of stabilized soil with only organic slurry, 4%.
A water swelling material is one of the rubbery impermeable materials which mixed synthetic resin elastomers as a base material, high absorbency polymers, filler and solvents. In this study, swelling characteristics of the water swelling material on the water polluted with COD and BOD, as an impermeable material at coastal waste landfill site, are examined by laboratory swelling ratio test. Furthermore, the factor in which it influences the swelling pressure of water swelling material is clarified by measuring the swelling pressure. As the results, the COD nor the BOD concentrations in the soaked water influence the swelling ratio of the water swelling material. When the thicknesses of water swelling material are 2 and 3mm, the maximum swelling pressure of 0.5 and 0.7MPa that correspond to hydraulic pressure by depth of 50 and 70 m is possessed, respectively.
This study investigated damage condition of a large GFRP tank used to dilute caustic soda. The tank was continuously used in a chemical factory for 13 years and finally scrapped. Samples for the investigation were obtained from four typical positions of the tank. For the samples, optical observation was conducted on the inside surface of the tank and on its cross-section in detail. The results showed that alkaline solution penetrated from fishnet-like cracks formed on the surface to the inside of GFRP. Formation of the cracks was thought to be caused by both deterioration of surfacing mats and cyclic stress due to change in temperature. The penetrated solution damaged chopped strand mats existing under the surfacing mats. Such damage condition was adequately predicted using ultrasonic echo data. Although the damage condition was different at each position of the tank, the bending strength was almost the same. That was because no damage reached to the filament winding layer to maintain the strength. The above results suggested that the investigated tank was suitably scrapped before a severe incident.
Carbon Fiber Reinforced Plastics (CFRP), which can reduce the weight of automotive, has become the centre of attention. From the view point of improving CFRP's recycling efficiency and productivity, there is a trend that Carbon Fiber Reinforced Thermoplastics (CFRTP) is used rather than Carbon Fiber Reinforced Thermoset Plastics. Polycarbonate (PC) has a high impact strength compared to other plastics, therefore in the near future, PC is expected to replace traditional materials for automotive parts. In this study, the vacuum assisted high speed compression molding method with electron magnetic induction heating system was proposed. The good impregnation of CF/PC at short time-frame, using low melt flow rate resin, can be molded by the vacuum assisted high speed compression molding method. The fiber/matrix interfacial share strength of CF/PC was much larger than these of CF/PA and CF/PP.
The particulate composite model derived to explain the high contact angle of water on the water repellent particulate composite materials was applied for the contact angle of other types of liquid such as methylene iodide and α-bromonaphthalene on the particulate composite materials. By substituting the experimental data of contact angle of water, methyleneiodide and α-bromonaphtalene to the formula of this model, following results were obtained. For water case, the more the PTFE volume fraction, the more area of PTFE surface is covered by air and that 100% of binder surface can be covered by water. For methylene iodide case, both PTFE and binder are covered thoroughly by methylene iodide for all the PTFE volume fraction. For α-bromonaphtalene case, the more the PTFE volume fraction, the more area of PTFE surface is covered by air and that 100% of binder surface can be covered by α-bromonaphtalene. By assuming that binder is covered by each of liquid, the contact angle of three different types of liquid on the PTFE particulate composites material can be skeptically expressed using the parameters of PTFE volume fraction and liquid coverage of PTFE.